For over half a century, a goal of materials characterization has been measuring impurity elements with high detection and atomic spatial resolution. Conventionally, a full understanding of materials issues such as dopant distributions, compositional uniformity, interface abruptness, grain boundary structure, impurity segregation, etc., is required to advance the technology of most materials to achieve the optimum performance.
Conventional methods of transmission electron microscopy (“TEM”) and scanning transmission electron microscopy (“STEM”) can provide two-dimensional sub-A structural information in thin specimens, but low-level chemical sensitivity from energy dispersive X-ray (“EDS”) and electron energy loss spectroscopy (“EELS”) is lacking and generally limited to approximately one percent. Secondary ion mass spectrometry (“SIMS”) is a proven technique for sampling one-dimensional low dopant levels (for example less than one ppm). Unfortunately, due to limitations in the spot size of the primary (sputtering) ion beam, spatial resolution with such systems is limited in the plane of the sample. Perpendicular to the sample (sputtering direction), the spatial resolution is greatly limited by forward scattering of the primary ion beam. When attempting to obtain low-level chemical information from nanostructures in electronic and optoelectronic materials, characterization techniques currently in use are fairly limited.